Lamp terminal structure and method of manufacture



8- 17, 1948- P. o. CARTUN LAIP TERIINAL STRUCTURE AND HOD 0F WUFACTUREFiled June 19, 1944 fVI/EN 70/2: PAL/L fl [ARR/N 51 [175 A7 THRIVE)Patented Aug. 17, 1948 UNITED STATES PATENT OFFICE LAMP TERMINALSTRUCTURE AND METHOD OF MANUFACTURE Paul 0. Cartun, Cleveland Heights,Ohio, assignor to General Electric Company, a corporation of New YorkApplication June 19, 1944, Serial No. 540,969

2 Claims; (01. 176-126) explained in connection with double-endedtubular discharge lamps of low-pressure positive column type, andparticularly fluorescent lamps of this character. The lamps particularlydescribed are of cold-starting type, having electrodes or cathodes whichare heated only by the energy of the discharge current, as exemplifiedin one known form by U. S. Patent No. 2,114,842 to Inman, and ascontrasted with the present commercial hot-starting fluorescent lamps,whose electrodes are specially preheated and rendered emissive ofelectrons before discharge between them is brought about, as describedin U. S. Patent No. 2,212,427 to Peters. The invention aims at providingsimple, strong, and eflicient structures; at facilitating thefabrication and processing of lamps; and at reducing costs. Variousother features and advantages of the'invention will appear from thedescription of species and forms of embodiment and from the drawings.

In the drawings, Fig. 1 shows a longitudinal section through one end ofa lamp constructed according to my invention; Fig. 2 is .plan view ofthe end unit of the lamp shown in Fig. l; and Fig. 3 is a tilted orperspective view of a lamp envelope tube and an end unit ready for beingsealed to one another in accordance with the invention.

Fig. 4 is a side view, partly sectional, of an end unit difierent fromthat shown in Figs. 1-3; and Fig. 5 is a side view of one end of a lampembodying the end unit shown in Fig. 4, with the end wall in section.

Fig. 6 is atilted or perspective view of one end of a lamp embodyingother modifications.

Fig. 7 is a tilted view of one end of a lamp illustrating still anothermodification.

As shown in Figs, 1 and 2, the discharge lamp L comprises a tubularenvelope in permeable to the light or other desired radiant output, andusually of vitreous material, such as the soft glass of whichfluorescent tubes are commonly made. Only one end of the lamp L appearsin the drawing; but in the'case of a double-ended tubular lamp, theconstruction shown may be substantially duplicated at the other end. Thewall II that closes in the end of the envelope l0 carries a mount l2including an electric energy translation device l3 which is here shownas an emissive cathode in the form of a coil or coiled coil of tungstenwire coated with activating oxide (5) such as an alkaline earth' mixtureincluding barium and strontium oxides. This emissive filament I3 may besupplemented with the usual unactivated anodes l4, l4, formed by ends ofthe current leads |5, |6 bent to extend parallel to the coil l3 and toone' another. As here shown, the envelope end is formed primarily by asheet metal disc to which the end of the tube I0 is sealed at IT,preferably by fusion of the material of the tube ill itself. The discmay be like those disclosed in U. S. Patents Nos. 2,146,579 to Inmanand2,158,849 to Blake, which serve as electrical contact terminals for thedevices on which they are used. The end disc H is shown as concavelydished for strength, has a narrow upturned lateral marginal flange '|8,and has a reentrant central hollow boss IQ of inverted conoidal form,which enlarges inward so as to provide an overhanging shoulder with, aperipheral groove 20 at the junction of the boss with the saucer-likeconcave portion of the disc. The disc may be made of the chrome-ironalloy known commercially as Allegheny 55, or of any other metal thatwill seal properly.

As shown in Figs. 1 and 2, the filament supporting current conductors orlead wires |5, [B of the mount l2 have suitably separated clamps 2|, 2|remote from the disc ll, between which the filament I3 is connected,while their portions nearer the disc are more closely spaced and aremechanically but. insulatively interconnected by means of a vitreousstem head 23 (which may be of glass like that of the tube I0), fused andsealed about the wires. The anodes |4, |4 may consist of extensions ofthe wires I5, l6 beyond the clamps 2|, 2|. Still nearer the disc H, theresilient conductor wire l5 may extend outward and downward. This wire[5 is firmly or rigidly attached and electricaly connected to the discpreferably by having its end portion bent into the form of a split ring25 encircling and elastically gripping the boss l9, at the bottom of itsperipheral groove 20. If desired, the wire ring 25 may be welded to theboss I! to provide a more perfect electrical and mechanical connectionto the disc II. The other conductor wire it has an extension 24 downwardand outward from beyond the insulative head 23 past the enlarged head ofthe boss l9 and past the disc H to the outside of the envelope ID, at ornear its seal I to the disc II. The wire It (or at least its portion 24that passes to the outside of the envelope l) should be of metal thatcan be sealed gas and vacuum-tight through the material that itDenetrates, such as the chrome-iron alloy of which the disc I I is made.As shown in Figs. 1, 2, and 3, the lead extension 24 is of wire muchfiner than the rest of the leads l5, l6, and is welded in the stouterpart of lead 16 below the bead 23. The fineness of the wire 24 givesgreater assurance of a satisfactory seal of this wire through thematerial at H. The disc ll may have a suitable opening to accommodatethe wire 24: as here ,4 terminal at each end, like .the disc ll shown inFigs. 1, 2, and 3, the heating is not so easy. To heat by a dischargebetween the cathodes at opposite ends of a lamp requires a much longertime than when it is done by passing current through each cathode. Toheat a cathode by a high-frequency coil outside .the lamp may bedifi'icult or shown, the disc margin or edge is arcuately notched out at26 to about the depth of the flange iii, to allow the wire 24 to extendthrough the seal material I! that attaches the disc II to the end of thetube I 0 without danger'of coming in contact with the disc.

Fig. 3 illustrates one preferred method of performing a sealing-inoperation to attach the end unit comprising disc II and mount l2 to theenvelope tube ID by fusion of the tube end, without the use of any othersealing material. As herevshown, the end of the tube l0 (reduced indiameter at a rounded shoulder 21 as is usual for envelope tubes offluorescent lamps) has been brought close to the disc II inaxialalignment therewith, the mount l2 extending into the tube, and thelead wire 24 extending out between the margin of the disc and the end ofthe tube, in or opposite the disc notch 26'. As shown in Fig. 3, thedisc H is apertured through the center of the boss l9 and carries anexhaust tube 28 sealed thereto around the aperture. The disc ll beingheated evenly and adequately by any suitable means (herediagrammatically represented by flames F playing on its side remote fromthe tube l0) the reduced end of the tube I0 is pressed against the hotdisc (or vice versa) until the tube end softens and fuses and seals tothe disc just inside the flange l8, whereupon the heating of the disc isdiscontinued to allow the glass to cool. While the end of the tube I0 isbeing pressed against the hot disc II to heat and fuse the tube, forceis applied to the wire 24 in the direction indicated by the arrow A inFig. 3, to shift the wire away from the disc into the softened materialof the tube end, and to hold the wire away from the disc II until thematerial has hardened and set. This completes a fused in-seal as shownin Fig. 1, with the lead wire 24 sealed gas and vacuum-tight through thein-seal portion of the envelope wall In out of contact with the disc.

In processing many electrical devices during manufacture, it isnecessary or convenient to heat their electric translation means afterbeing sealed into the envelope of the device, as an incident ofexhausting, gettering, gas-charging, or otherwise treating the device orits translation means. In the case of discharge devices, this isnecessary in order to degas the electrodes; and in the case of activatedcathodes, it is particularly necessary to convert or transform materialthat has been applied to them before sealing-in into the desiredemissive material or condition, and to get rid of gas or vapor evolvedin the transformation. In the case of ordinary hot-starting fluorescentlamps having a pair of current leads for each cathode, which are used inpreheating the cathodes before starting the operating discharge in thelamp, these leads are available for passing heating current through thecathodes during the processing just referred to; but in the case offluorescent lamps having but a single contact impracticable because ofthe fineness of many filamentary cathodes. But by providing the mount l2with an extra lead l6 extended out at 24 through the envelope wall orend seal as described, resistance heating of the cathode by passingcurrent through it as indicated diagrammatically in Fig. 1 becomespracticable and easy. After this has been done, the extent or projectionof the external portion of the lead 24 beyond its seal may be reduced,as explained hereinafter, so that it cannot get in the way or give anytrouble in a lamp socket (not shown). The lamp end may be completed bysealing off the exhaust tube 28 inside the recess afforded by the boss19 as indicated at 3| in Fig. 1, so that the seal is well sheltered andprotected in the recess.

The end unit l2 shown in Figs. 4 and 5 differs from that in Figs. 1, 2,3 in that the edge of the disc Ila has no upturned flange I 8 as inFigs. 1-3 and no notch 26, and in that the lead "5a is of the same sizeas the lead [5 throughout. Also, the disc Ila is without the exhausthole and tube 28 of Fig. 3. As shown in Fig. 4, the lead l5 extendsupward on a steeper slope than in Figs. 1 and 3, so that the mount [2 istilted to the left somewhat, and the lead I'Sa clears the disc edge byan ample distance. When, therefore, the envelope tube I0 is pressedagainst the disc Ila as above described in connection with Fig. 3, thelead I5 is elastically flexed to the right and downward (as Fig. 4 isdrawn) by the pressure of the tube end. As the tube end softens underthe heat of the disc I la, the lead l5 unfiexes elastically and pushesthe lead I 6a upward and sidewise through the soft glass enough to shiftor keep the lead lBa away from the edge of the disc, and the seal coolsoff with the mount 12 in proper position and with the lead llia out ofcontact with the disc edge, as shown in Fig. 5. After the lampprocessing which requires use of the lead lBa to heat the translationmeans l3, as above described, the extent or projection of lead Iliaoutside the envelope I 0 may be reduced by cutting the wire off at orclose to the latter, or by bending any short protruding wire end upagainst the envelope wall below the shoulder 21, as shown in Fig. 5 at32, or both.

Fig. 6 illustrates a mount l2b in which the parts are arrangeddifferently from what is shown in Figs 1-5: i. e., the lead wire I6?) isinsulatively connected to the lead wire I5b by the bead 23b directly inline with the wire l5b, instead of alongside it as in Figs. 1-5; and thealkaline earth oxide-activated filament coil cathode l3b extends axiallyof the envelope tube l0, instead of crosswise, being connected betweenclamps at the ends of lateral branches 33, 34 of the leads 15b, lBb,consisting of short wires welded to the latter. The lead wire I6b hasanother branch 24b that extends rearward and alongside the standardformed by wires lGb, l5b and bead 23b, and passes to the outside of theenvelope II) at or adjacent the seal l1. As shown, this branch 24b is offine wire like the lead extension 24 in Figs. 1-3, being welded at oneend of the junction of wire 34 with wire "$12, and being bent (in aZ-configuration) to extend out through the envelope wall. An

anode disc b is shown arranged transversely of the envelope l coaxiallytherewith and in front of the translation means or filament [3b, and isconnected to the inner end of the latter through the lead I62) and itsbranch. The disc llb may conveniently be supported by means of the lead1 5b, which is shown as having its upper end bent to extend radiallyinward and welded to the rear face of the disc. To avoid having the discll function as anode, rather than the disc l'lb connected to disc llthrough the resistance of filament 131), the disc ll may be coveredwholly or nearly completely with suitable insulation. This does notnecessarily mean a complete vitreous end wall for the envelope l0 insidethe disc I l, or an insulative coating covering the inner side of disc II; on the contrary, a thin disc of insulation 35 such as mica may besuitably interposed between the disc II and the cathode lib, being asshown threaded around the wire l5b to lie against the boss l9 and theenvelope and disc joint 11, inside the lead wire 241).

With this arrangement, substantially the whole discharge current goes tothe disc 24b and traverses' the cathod filament l3b during each anodecycle at this end of the lamp L (when the lamp is operating on A. 0.),thus heating the filament. By making the filament wire l3b of propergauge and resistance, it can be resistanceheated in this manner on theanode cycles sufficiently to make it emit thermionically on the cathodecycles all the electrons required to carry the discharge current in thelamp L, without necessity for any heating by the discharge on thecathode cycles, although there is, generally, some current flow throughat least part of the filament |3b on the cathode cycles, and someconsequent resistance-heating of the filament during these cycles. Bymaking the anode disc Nb of suitable size, the anode drop during theanode cycles can be minimized or reduced virtually to zero, thusminimizing the energy in the discharge at this time, and alsoeliminating voltage oscillations at the anode. For a (SO-wattfluorescent lamp H operating with a discharge current of 0.4 ampere andhaving a 1-inch T-8 tube 6 feet long for its envelope It), a disc Nb of5 mil sheet molybdenum or iron about inch in diameter is satisfactory,and the filament lib may consists of 100 mm. length of tungsten wire of1.83 mil size wound 347 turns per inch on a mandrel of 4 mil size forits primary winding; and for a coiled coil, this mandrel with itswinding maybe wound 70 turns per inch on a 16.1 mil mandrel, givingabout 8 turns of secondary winding. After suitable heattreatment to setthe coils, both mandrels may be removed by dissolving them out as usual.With these dimensions, half the energy traverses the filament 13b on theanode cycles of the electrode.

Fig. 7 shows a mount essentially like that in Figs. l-3, but illustratesa variation from Figs. 1-6 as regards the way in which the lead wire 240is brought out. Instead of extending past the outer disc edge It as inall of Figs 1-6, the lead 24c extends through a round hole 280 piercedin the disc H and closed by a suitable seal around the wire: in otherwords, the disc opening for the wire He has the form of a hole insteadof a notch as in Figs. 1-3. As here shown, the hole 200 is in the discmargin near enough to the disc edge It to be covered and sealed uparound the wire 24c by the material forming the end seal l1 between thetube 10 and the disc l'l when the tube end is pressed and fused to thedisc as described in connection with Figs. 1-3. Thus the use of a discopening 260 in the form of a hole need not entail any extra sealingoperation, nor need any lateral pressure be exerted onthe wire 24cduring the sealing as in Figs. 1-6: all that is necessary is to hold thewire centered in the hole 260 when forming the seal H.

In order to dispense with repetitive description, various parts andfeatures in Figs. 4-7 are marked with the same reference numerals astheir homologues in earlier figures, a distinctive letter being addedwhere such distinction seems needful.

I make no claim herein for the special mount and electrode featuresillustrated in Fig. 6, as distinguished from those in Figs. 15, sincethese features of Fig. 6 form no part of my present invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An end unit for an enevolpe of the character described comprising ametal end disc, for scaling to the envelope end, having a lateralmarginal flange with a notch in said flange, and a filament mountingstructure carried by said disc comprising current conductors havingseparated filament clamps remote from the disc and also having portionsnearer the disc more closely spaced, with an insulative stem bead sealedto and mechanically but insulatively interconnecting said portions ofsaid conductors, one of said conductors being attached and electricallyconnected to said disc, and the other conductor extending outward pastthe edge of the disc opposite said notch, in position to be insulativelyembedded in and extend out through an insulative seal by which said discmay be attached to an envelope end.

2. A method of fabricating an electrical device comprising aradiation-transmitting envelope with a metal end disc carrying a mountin the envelope including a resilient conductor attached andelectrically connected to said disc, an associated conductormechanically but insulatively connected to the foresaid conductor, and afilament connected between said conductors; which method comprisesplacing the open end of the envelope around the mount adjacent the disc,with said associated conductor extending out between the envelope endand the edge of the disc; bringing said envelope end to the disc andsealing it thereto; and pressing said outward extending associatedconductor toward the enevelope end away from the disc while the seal issoft.

PAUL O. CARTUN.

REFERENCES CITED The following references are of record in the file ofthis patent;

UNITED STATES PATENTS Number Name Date 1,205,002 Marshall Nov. 14, 19161,972,125 Anderson Sept. 4, 1934 2,146,579 Inman Feb. 7, 1939 2,177,498Payne Oct. 24, 1939 2,359,483 Kuebler Oct. 3, 1944 FOREIGN PATENTSNumber Country Date 499,120 Great Britain Jan, 18, 1939

